It is desirable to patch holes and cracks in walls with gypsum cement. Heretofore there have been certain problems in applying gypsum cements to non-horizontal surfaces. When gypsum cement is mixed with water it is initially too fluid to trowel onto the non-horizontal surface. When the gypsum cement has set sufficiently to be troweled onto the non-horizontal surface the water in the mixture will "wick away" from the mixture into the porous or water wetable surface being patched. Hydroxyethyl ethers of cellulose and methylcellulose have been used with some success to thicken gypsum cement mixtures to prevent the water from "wicking away". Guar gum has been used with certain gypsum cement. The guar gum prevented "wicking away" but also flocculated the gypsum cements thus producing a weak set. Hydroxyalkyl ethers of guar have been mixed with plaster of paris. While the hydroxyalkyl ethers of guar do not flocculate the gypsum cement as does guar gum, the hydroxyalkyl ethers of guar thickens so rapidly the gypsum cement cannot fully wet out before the thickening occurs. This feature results in producing a poor final set.